02.08 - Membranes and Transport Systems

Question 1

Which of the following cellular components is not defined by an internal membrane?

a. Peroxisomes
b. Lysosomes
c. Golgi apparatus
d. Centrosome

Answer 1

d. Centrosome

Question 2

Which of the following statements in incorrect?

a. Lipids are asymmetrically distributed in cellular membranes.
b. Flippase facilitates side-to-side movement of phosphatidylserine and phosphatidylethanolamine.
c. Floppase is non-specific, outward-directed, and ATP-dependent.
d. None of the above

Answer 2

d. None of the above

Question 3

Which of the following decreases membrane fluidity?

a. Increased temperatures
b. Kinks introduced by unsaturated fatty acids
c. Trans fatty acids
d. None of the above

Answer 3

c. Trans fatty acids (straighter compared to the cis form, results in a more rigid membrane)

Question 4

What increases membrane permeability to water and other small, hydrophilic molecules?

a. Increased membrane fluidity
b. Increased temperatures
c. Interactions between hydrophobic tails
d. A and B

Answer 4

d. A and B

Question 5

Which of the following does not apply to cholesterol?

a. It is a steroid and is lipid-soluble.
b. It can be found only in the outer leaflet of the lipid bilayer.
c. It is synthesised in the ER and is amphipathic.
d. It is considered to be a membrane fluidity buffer.

Answer 5

b. It can be found only in the upper leaflet of the lipid bilayer.

Question 6

What phospholipid is the precursor of sphingomyelin?

Answer 6

Phosphatidylcholine

Question 7

What phospholipid is composed of 24 carbon and insulates nerve fibbers?

Answer 7

Sphingomyelin

Question 8

Which of the following statements is true about glycolipids?

a. It is the least common of membrane lipids.
b. It is always found in the outer leaflet of the membrane.
c. It is an antigenic determinant of red blood cells.
d. All of the above.

Answer 8

d. All of the above.

Question 9

Which of the following statements in incorrect?

a. Integral proteins are synthesised in the rough ER.
b. Integral proteins can only be removed by disrupting the lipid bilayer.
c. Peripheral proteins are not covalently linked to other membrane components.
d. Extracellular peripheral proteins are synthesised in the Golgi apparatus and is exocytosed.

Answer 9

d. Extracellular peripheral proteins are synthesised in the Golgi apparatus and is exocytosed. (Extracellular peripheral proteins are produced in the ER.)

Question 10

These are groups of integral membrane proteins that contain cave-in and can function as a transcellular pathway or signalling process.

Answer 10

Caveolae

Question 11

These are intercellular junctions that serves as a barrier to prevent molecules and ions to move freely between cells.

Answer 11

Tight junctions

Question 12

_______________ are specialised regions in the plasmalemma composed of lipids such as cholesterol and sphingomyelin and function in signalling.

Answer 12

Lipid rafts

Question 13

What do you expect to easily diffuse into the cell membrane?

a. Oxygen
b. Carbon dioxide
c. Sodium
d. A and B

Answer 13

d. A and B

Question 14

Which of the following statements is incorrect?

a. Endocytosis occurs preferentially at clathrin-coated pits.
b. Pinocytosis refers to the ingestion of small particles.
c. Gap junctions allow the direct flow of molecules from one cell to another.
d. None of the above.

Answer 14

d. None of the above.

Question 15

Passive transport:

a. Does not require energy.
b. Is driven by intrinsic kinetic energy of molecules.
c. May be selective.
d. All of the above.

Answer 15

d. All of the above.

Question 16

Which of the following statements is incorrect?

a. The Na/K pump maintains the low intracellular K concentration in intestinal cells.
b. In active transport, movement of solutes is coupled to ATP hydrolysis.
c. Glucose flows passively out of intestinal cells through the GLUT2 transporter.
d. The co-transport of Na and glucose through SGLT1 is an example of secondary active transport.

Answer 16

a. The Na/K pump maintains the low intracellular K concentration in intestinal cells. (The Na/K pump maintains low intracellular Na concentration!)

Question 17

Which type of primary active transporter is dephosphorylated during the transport of Na, K or Ca?

Answer 17

P-type transporter

Question 18

These are proton pumps responsible for the acidification of the interior of lysosomes, endosomes and Golgi vesicles.

Answer 18

V-type transporter

Question 19

These transporter translocates protons at the expense of ATP hydrolysis in the mitochondria.

Answer 19

F-type transporter

Question 20

Which of the following statements is incorrect?

a. Sulfonylurea receptor is an atypical ABC transporter that indirectly regulates potassium channels.
b. Secondary active transport utilizes a secondary source of energy such as a transmembrane electrochemical gradient of Na or H.
c. Carrier proteins changes shape to facilitate entry and exit of substances.
d. None of the above.

Answer 20

d. None of the above.

Question 21

These are ion carriers or channels produced by microorganisms.

Answer 21

Ionophores

Question 22

Which of the following statements is true?

a. Carriers exhibit saturation kinetics with respect to solute concentration.
b. Carriers exhibit sterospecificity.
c. Carriers are susceptible to inhibition and hormonal control.
d. All of the above

Answer 22

d. All of the above

Question 23

Which of the following statements is true?

a. GLUT is a transmembrane protein with a fixed topology.
b. Aquaporins are small, hydrophilic proteins with highly conserved AA sequences.
c. Gramicidin channels have alternating D & L carbohydrates.
d. A and B

Answer 23

a. GLUT is a transmembrane protein with a fixed topology.

Question 24

What disease is caused by mutations in the gene encoding for aquaporin (AP-2) and is characterised by polyuria due to lack of water absorption?

Answer 24

Nephrogenic diabetes insipidus

Question 25

Which of the following statements is incorrect?

a. Cellular channels usually consist of large protein complexes with transmembrane alpha helices.
b. The control of channel gating is a form of allosteric regulation.
c. Channels cycle between open and closed conformations; when open, it provides a continuous pathway through the bilayer.
d. None of the above

Answer 25

d. None of the above

Question 26

True or False: There is a higher transport rate in channels compared to carriers.

Answer 26

True.

Question 27

Which is incorrectly paired?

a. Phagocytosis - entire cell is engulfed
b. Pinocytosis - external fluid is engulfed
c. Endocytosis - large molecules are released through the cell membrane
d. None of the above

Answer 27

c. Endocytosis - large molecules are released through the cell membrane

Question 28

Achondroplasia is caused by a mutation in which gene?

Answer 28

Fibroblast growth factor 3 (FGFR3)

Question 29

Patients with achondroplasia:

a. Exhibit short-limbed dwarfism
b. Are deficient in the receptor that responds to bone ossification growth factors
c. Fail to convert cartilage into bone
d. All of the above

Answer 29

d. All of the above

Question 30

A genetic mutation in the low density lipoprotein (LDLR) gene:

a. Reduces the production of LDLR, causing very low cholesterol levels
b. Results in the inability to transport LDL into the cell
c. May be a cause of familial hpercholesterolemia
d. B and C

Answer 30

d. B and C

Question 31

It is the autosomal recessive disease that results from the accumulation of mucus in cilia due to a defective chloride ion channel.

Answer 31

Cystic fibrosis

Question 32

It is an autosomal recessive disorder that results from the accumulation of copper due to a defect in the ATPase that transports copper ions from the liver to the bile canaliculi.

Answer 32

Wilson disease

Question 33

Interaction of cancer cells with oligosaccharides in the cell membrane results in ___________.

Answer 33

Metastasis